Photographic light-sensitive materials are generally composed of light-sensitive photographic emulsion layers and light insensitive layers such as an interlayer, an emulsion protective layer, a filter layer, or an antihalation layer applied, directly or indirectly through a subbing layer, to one side or both sides of the support consisting of, for example, an .alpha.-olefin such as polystyrene or polyethylene, a cellulose ester such as cellulose acetate or nitrocellulose, a polyester such as polyethylene terephthalate or polyethylene napththalate, paper, or a synthetic paper. In light-sensitive materials such as color photographic elements, auxiliary layers such as an antistatic layer, a curl preventing layer, a magnetic recording layer, a barrier layer, a scratch resistant overcoat layer, or a surface lubricant layer, are provided on the back side of the support in order to enhance the photographic or physical quality of the photographic light-sensitive materials.
The need to provide photographic film and paper with antistatic protection has long been recognized. Such protection is important since the accumulation of static charges as a result of various factors in the manufacture, finishing, and use of photographic elements is a serious problem in the photographic art. Accumulation of static charges can result in fog patterns in photographic emulsions, various coating imperfections such as mottle patterns and repellency spots, dirt and dust attraction which may result in the formation of "pinholes" in processed films, and a variety of handling and conveyance problems.
To overcome the problem of accumulation of static charges it is conventional practice to provide an antistatic layer (i.e., an electrically conductive layer) in photographic elements. A very wide variety of antistatic layers are known for use in photographic elements. For example, an antistatic layer comprising an alkali metal salt of a copolymer of styrene and styrylundecanoic acid is disclosed in U.S. Pat. No. 3,033,679. Photographic films having a metal halide, such as sodium chloride or potassium chloride, as the conducting material, in a hardened polyvinyl alcohol binder are described in U.S. Pat. No. 3,437,484. In U.S. Pat. No. 3,525,621, the antistatic layer is comprised of colloidal silica and an organic antistatic agent, such as an alkali metal salt of an alkylaryl polyether sulfonate, an alkali metal salt of an arylsulfonic acid, or an alkali metal salt of a polymeric carboxylic acid. An antistatic layer comprised of an anionic film forming polyelectrolyte, colloidal silica and a polyalkylene oxide is disclosed in U.S. Pat. No. 3,630,740. In U.S. Pat. No. 3,681,070, an antistatic layer is described in which the antistatic agent is a copolymer of styrene and styrene sulfonic acid. U.S. Pat. No. 4,542,095 describes antistatic compositions comprising a binder, a nonionic surface-active polymer having polymerized alkylene oxide monomers and an alkali metal salt. In U.S. Pat. No. 4,916,011, an antistatic layer comprising a styrene sulfonate-maleic acid copolymer, a latex binder, and an alkyl-substituted trifunctional aziridine crosslinking agent is disclosed. An antistatic layer comprising a vanadium pentoxide colloidal gel is described in U.S. Pat. No. 4,203,769. U.S. Pat. Nos. 4,237,194, 4,308,332, and 4,526,706 describe antistats based on polyaniline salt-containing layers. Crosslinked vinylbenzyl quaternary ammonium polymer antistatic layers are described in U.S. Pat. No. 4,070,189.
The surface lubricant layer is normally applied as the outermost layer, as is the case for a backing layer. It is desirable for this layer to have a low coefficient of friction (COF) to provide proper conveyance properties and to protect the imaging elements from mechanical damage during the manufacturing process or customer use. It is known to protect imaging elements against mechanical damage by coating them with a layer comprising a lubricant such as a wax. However, it has proven difficult to provide a single layer applied from organic medium that comprises both an antistatic agent and a lubricant since it is difficult to find a coating medium that dissolves both the antistat and the lubricant and is at the same time attractive from an environmental and health standpoint. In addition, it is difficult to form a stable dispersion of a lubricant such as a wax in an organic medium that may be added to a coating composition containing an antistatic agent. Therefore, in order to form a backing layer which can be applied from liquid organic medium that is both conductive and has a low coefficient of friction one often applies two separate layers; a first layer which is comprised of an antistatic agent and then a second layer which is comprised of a lubricant such as a wax.
It is always desirable to have a backside protective overcoat that serves as many functions as possible in order to reduce manufacturing complexity and cost. It is also desirable to have such a layer formed by coating and drying from coating compositions based on solvents that are less hazardous to the environment.
An objective of the invention is to provide image elements with an antistatic layer comprising an ionic conductive polymer having improved manufacturability and surface characteristics.